1. Field of the Invention
The present invention relates to a fuel injection valve which injects fuel into an internal combustion engine, and relates to an art for forming an excellent fuel spray with regard to ignition property and combustion property.
2. Conventional Art
As an alternative of an in-intake manifold fuel injection device which injects fuel into an intake manifold of an internal combustion engine, an in-cylinder fuel injection device is known which injects fuel directly into a combustion chamber.
JP-A-6-146886(1994), for example, discloses such in-cylinder gasoline injection engine. In this conventional art, with consideration with regard to attachment position of a fuel injection valve and with formation of an intake flow of vertical swirl (tumble flow) in a combustion chamber through an intake port extending upward from an intake opening end, combustion is performed stably with leaner fuel than that at stoichiometric air fuel mixture and fuel economy is improved.
However, the above conventional art did not necessarily take into account fully of a spray shape or a spray structure which can improve both an ignition property (firing property) and a combustion property (reduction of unburnt gas exhaust amount), which will be explained hereinbelow.
In order to optimize a spray injected from a fuel injection valve, it is necessary to take into account of the following characteristics. First one is a spray shape of which influence factors are a spreading angle of the spray and a reaching distance thereof. Second one is a spray particle diameter, in that it is necessary to uniformalize the particle diameter distribution while reducing number of particles having large diameters as much as possible. Third one is a spray structure which is required to optimize a space distribution of the sprayed fuel particles.
As a result of experimental analysis and study with regard to how these spray characteristics affect combustion characteristics for the internal combustion engine, the followings are clarified. In order to improve an ignition property, it is effective to increase fuel particle distribution around an ignition unit and to enhance distribution of air fuel mixture of combustible density. On the other hand, if a fuel particle distribution in a piston direction is reduced, unburnt gas components (HC, CO) in the fuel tend to decrease, thereby, the combustion property is improved. Further, in order to obtain a combustion stability over a broad range from a low engine rpm to a high engine rpm, it is preferable that the spray shape does not vary by a variation of pressure in the cylinder. This is because since the geometric positional relationship between a fuel injector and an ignition unit is fixed, in order to always supply a fuel spray of a proper density to the ignition unit it is important to keep the fuel spray expansion constant. In other words, a fuel spray injected by a conventional fuel injector tends to spread, when pressure in a cylinder is low and tends to be collapsed, when the pressure in the cylinder is high. Therefore, if the arrangement of the fuel injector and the ignition unit is determined with reference to a comparatively high pressure condition of the cylinder, the fuel tends to deposit on an upper and side cylinder face in the cylinder or on a piston head, when the pressure in the cylinder lowers, on the other hand, if a comparatively low pressure condition in the cylinder is selected as a reference, it tends to be difficult to reach fuel spray suitable for combustion to the ignition unit when pressure in the cylinder rises.
The present invention is to provide a fuel injection valve and an internal combustion engine mounting the same which improves the ignition property of the internal combustion engine and realizes a fuel spray suitable to reduce the exhaust amount of unburnt gas components at the time of the combustion.
In order to achieve the above object, a fuel spray is produced of which shape is hardly varied with respect to pressure variation in the cylinder. For this purpose, such a fuel spray is generated that the air fuel mixture toward the ignition unit is converged and fuel particles toward a piston is leaned. At this instance, air outside the spray is introduced into the spray from portions where the fuel particles is leaned (or where fuel molecules are exhausted). Thereby, a pressure difference between outside and inside the spray can be reduced which makes difficult to collapse the spray.
Specifically, at an outlet port of an injection hole which is provided at a fuel injection valve and is for injecting fuel, through removing a part of a wall face forming the injection hole it is preferable that a restriction to a spray flow is released and a deflecting spray is formed in which the spray at the side where the restriction is released is rich and that at the side restricted is lean. In this instance, it is also preferable to vary the restriction force non-linearly.
In an internal combustion engine, it is preferable to arrange the above fuel injection valve in such a manner that a rich spray is formed at the side of the ignition unit and a lean spray is formed at the side of the piston.